U.S. patent number 6,577,379 [Application Number 09/993,053] was granted by the patent office on 2003-06-10 for method and apparatus for shaping and/or orienting radiation irradiating a microlithographic substrate.
This patent grant is currently assigned to Micron Technology, Inc.. Invention is credited to Ulrich C. Boettiger, Scott L. Light.
United States Patent |
6,577,379 |
Boettiger , et al. |
June 10, 2003 |
Method and apparatus for shaping and/or orienting radiation
irradiating a microlithographic substrate
Abstract
A method and apparatus for shaping and/or orienting radiation
irradiating a microlithographic substrate. The method can include
directing a beam of radiation along a radiation path toward a
reflective medium, with the beam having a first shape in a plane
generally transverse to the radiation path. The shape of the
radiation beam can be changed from the first shape to a second,
different shape by inclining a first portion of the reflective
medium relative to a second portion of the reflective medium and
reflecting the radiation beam toward a microlithographic substrate.
The beam can then impinge on the microlithographic substrate after
changing the shape from the first shape to the second shape, and at
least a portion of the radiation can be inclined relative to the
radiation path, for example, to enhance the imaging of selected
diffractive orders.
Inventors: |
Boettiger; Ulrich C. (Boise,
ID), Light; Scott L. (Boise, ID) |
Assignee: |
Micron Technology, Inc. (Boise,
ID)
|
Family
ID: |
25539039 |
Appl.
No.: |
09/993,053 |
Filed: |
November 5, 2001 |
Current U.S.
Class: |
355/52 |
Current CPC
Class: |
B82Y
10/00 (20130101); G03B 27/68 (20130101); G03F
7/70116 (20130101); G03F 7/70166 (20130101); G03F
7/702 (20130101) |
Current International
Class: |
G03B
27/68 (20060101); G03B 027/68 () |
Field of
Search: |
;355/51,52,53,60,66 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
US. patent application Ser. No. 09/945,167, Boettiger et al., filed
Aug. 30, 2001. .
U.S. patent application Ser. No. 09/945,316, Boettiger et al.,
filed Aug. 30, 2001. .
Fukuda, H. et al., "Improvement of defocus tolerance in a
half-micron optical lithography by the focus latitude enhancement
exposure method: Simulation and experiment," J. Vac. Sci. Technol
B. vol. 7 No. 4, Jul./Aug. 1989, pp. 667-674, 8 pages. .
Texas Instruments Incorporated, "What the Industry Experts Say
About Texas Instruments Digital MicroMirror Display (DMD)
Technology," 6/94, (2 pages). .
Optics. ORG, Industry News, "Micronic and Fraunhofer Develop New
Pattern Generators," Posted: Dec. 10, 1999 (1 page)..
|
Primary Examiner: Adams; Russell
Assistant Examiner: Esplin; D. Ben
Attorney, Agent or Firm: Perkins Coie LLP
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application relates to material disclosed in U.S. application
Ser. No. 09/945,167 titled "Method and Apparatus for Irradiating a
Microlithographic Substrate" and filed on Aug. 30, 2001; and U.S.
application Ser. No. 09/945,316 titled "Method and Apparatus for
Controlling Radiation Beam Intensity Directed to Microlithographic
Substrates" and filed on Aug. 30, 2001; both incorporated herein in
their entireties by reference.
Claims
What is claimed is:
1. A method for irradiating a microlithographic substrate,
comprising: directing a beam of radiation along a radiation path
toward a reflective medium having a reflective surface, the beam of
radiation having a first shape and a first intensity uniformity in
a plane generally transverse to the radiation path; changing a
shape of the radiation beam from the first shape to a second shape
different than the first shape by inclining a first portion of the
reflective surface relative to a second portion of the reflective
surface and reflecting the beam from the reflective surface toward
a microlithographic substrate, the beam with the second shape
having a second intensity uniformity less than the first intensity
uniformity; and impinging the beam on the microlithographic
substrate after changing the shape from the first shape to the
second shape.
2. The method of claim 1, further comprising changing an angle of
at least a portion of the radiation relative to the radiation path
by passing the radiation beam through an optical element after
changing the shape of the beam from the first shape to the second
shape.
3. The method of claim 1 wherein the radiation beam has a first
intensity prior to impinging on the reflective surface, and wherein
the method further comprises: directing the radiation beam away
from the reflective surface with the second shape and with a second
intensity at least approximately the same as the first intensity;
and changing an angle of at least a portion of the radiation
relative to the radiation path by impinging the radiation beam on
an optical element after changing the shape of the beam from the
first shape to the second shape.
4. The method of claim 1 wherein the first portion of the
reflective surface forms a smooth, continuous surface with the
second portion of the reflective surface, and wherein moving the
first portion of the reflective surface includes moving one portion
of the continuous surface relative to another.
5. The method of claim 1, further comprising selecting the
radiation to have a wavelength of from about 13 nanometers or less
to about 365 nanometers.
6. The method of claim 1 wherein the first portion of the
reflective surface includes a first reflective element and the
second portion of the reflective surface includes a second
reflective element, and wherein moving the first portion includes
moving the first element relative to and independently of the
second element.
7. The method of claim 1, further comprising scanning the reticle
and the microlithographic substrate relative to each other by
moving the reticle along a reticle path generally normal to the
radiation path proximate to the reticle and moving the
microlithographic substrate along a substrate path in a direction
opposite the reticle and generally normal to the radiation
path.
8. The method of claim 1, further comprising stepping the
microlithographic substrate and the reticle relative to each other
by impinging the radiation on a first field of the
microlithographic substrate while the microlithographic substrate
is in a fixed transverse alignment with the reticle, moving at
least one of the reticle and the microlithographic substrate
transversely relative to the other to align a second field with the
reticle, and exposing the second field to the radiation.
9. The method of claim 1 further comprising exposing a
radiation-sensitive material of the microlithographic substrate to
the radiation beam.
10. The method of claim 1, further comprising exposing a layer of
photoresist material on the microlithographic substrate to the
radiation beam.
11. The method of claim 1, further comprising: directing the
radiation with the second shape along the radiation path toward the
microlithographic substrate; ceasing to impinge the radiation on
the microlithographic substrate while changing a position of the
first portion of the reflective surface relative to the second
portion; and directing radiation with a third shape different than
the second shape from the reflective surface and toward the
microlithographic substrate.
12. The method of claim 1, further comprising changing the shape of
the radiation beam from the second shape to a third shape different
than the second shape while the radiation beam impinges on the
microlithographic substrate by moving at least one of the first and
second portions of the reflective surface relative to the
other.
13. The method of claim 1 wherein changing a shape of the radiation
beam from a first shape to a second shape different than the first
shape includes changing the shape to at least one of an annular
shape, a dipole shape and a quadrupole shape.
14. The method of claim 1, further comprising changing an intensity
of a first portion of the radiation beam in a plane generally
transverse to the radiation path relative to a second portion of
the radiation beam in the same plane.
15. The method of claim 1 wherein changing the shape of the
radiation beam from a first shape to a second shape includes
changing the shape of the radiation beam to a second shape having a
major axis and a minor axis, and wherein the method further
comprises: directing the radiation beam with the second shape along
the radiation path toward an aperture of a reticle, the aperture
having a major axis and a minor axis; and aligning the major axis
of the second shape of the radiation beam to be at least
approximately parallel with the major axis of the aperture.
16. The method of claim 1, further comprising directing the beam
through apertures of a reticle before impinging the beam on the
microlithographic substrate.
17. The method of claim 1, further comprising directing the beam
through apertures of a reticle after changing the shape of the
radiation beam.
18. The method of claim 1 wherein changing the shape of the
radiation beam from a first shape to a second shape includes
changing from a first shape having a cross-sectional area with a
first diameter to a second shape having a cross-sectional area with
a second diameter different than the first diameter.
19. The method of claim 1, further comprising: directing the
radiation beam through a diffuser and toward a collecting lens;
passing the radiation beam through the collecting lens to incline
at least part of the radiation beam relative to the radiation path;
and directing the radiation beam to impinge on the
microlithographic substrate, with at least part of the radiation
beam inclined relative to the radiation path.
20. A method for irradiating a radiation-sensitive material of a
microlithographic substrate, comprising: directing a beam of
radiation along a radiation path toward a reflective surface, the
beam of radiation having a first shape and a first intensity
uniformity in a plane generally transverse to the first direction,
the beam of radiation further having a first intensity; changing a
shape of the radiation beam from the first shape to a second shape
different than the first shape by inclining a first portion of the
reflective surface relative to a second portion of the reflective
surface and reflecting the beam from the reflective surface toward
a microlithographic substrate, the beam with the second shape
having a second intensity uniformity less than the first intensity
uniformity; directing the radiation beam away from the reflective
surface with a second intensity at least approximately the same as
the first intensity; changing an angle of at least a portion of the
radiation beam relative to the radiation path by impinging the
radiation beam on a reflective or refractive optical element after
changing the shape of the beam from the first shape to the second
shape; impinging the beam on a reticle; and impinging the beam on
the radiation sensitive material of the microlithographic substrate
after changing the shape from the first shape to the second shape
and after impinging the beam on the reticle.
21. The method of claim 20, further comprising: changing an angle
of a first portion of the radiation beam relative to the radiation
path from a first value to a second value; changing an angle of a
second portion of the radiation beam relative to the radiation path
from the first value to a third value different than the second
value; and impinging the radiation beam on the microlithographic
substrate with the first portion having a first intensity and the
second portion having a second intensity different than the first
intensity.
22. The method of claim 20, further comprising scanning the reticle
and the microlithographic substrate relative to each other by
moving the reticle along a reticle path generally normal to the
radiation path proximate to the reticle and moving the
microlithographic substrate along a substrate path in a direction
opposite the reticle and generally normal to the radiation
path.
23. The method of claim 20 further comprising stepping the
microlithographic substrate and the reticle relative to each other
by impinging the radiation on a first field of the
microlithographic substrate while the microlithographic substrate
is in a fixed transverse alignment with the reticle, moving at
least one of the reticle and the microlithographic substrate
transversely relative to the other to align a second field with the
reticle, and exposing the second field to the radiation.
24. The method of claim 20, further comprising exposing a layer of
photoresist material on the microlithographic substrate to the
radiation beam.
25. The method of claim 20, further comprising: directing the
radiation with the second shape along the radiation path and toward
the microlithographic substrate; ceasing to impinge the radiation
on the microlithographic substrate while changing a position of the
first portion of the reflective surface relative to the second
portion; and directing from the reflective surface and toward the
microlithographic substrate radiation with a third shape different
than the second shape.
26. The method of claim 20, further comprising changing the shape
of the radiation beam from the second shape to a third shape
different than the second shape while the radiation beam impinges
on the microlithographic substrate by moving at least one of the
first and second portions of the reflective surface relative to the
other.
27. The method of claim 20 wherein changing a shape of the
radiation beam from a first shape to a second shape different than
the first shape includes changing the shape to at least one of an
annular shape, a dipole shape and a quadrupole shape.
28. The method of claim 20, further comprising changing an
intensity of a first portion of the radiation beam in a plane
generally transverse to the radiation path relative to a second
portion of the radiation beam in the same plane.
29. The method of claim 20 wherein changing the shape of the
radiation beam from a first shape to a second shape includes
changing the shape of the radiation beam to a second shape having a
major axis and a minor axis, and wherein the method further
comprises: directing the radiation beam with the second shape along
the radiation path through the aperture of the reticle, the
aperture having a major axis and a minor axis; and aligning the
major axis of the second shape of the radiation beam to be at least
approximately parallel with the major axis of the aperture.
30. A method for irradiating a radiation-sensitive material of the
microlithographic substrate, comprising: directing a beam of
radiation having a first intensity uniformity toward a reticle
positioned to pass zeroth diffraction order radiation in a first
direction toward the microlithographic substrate, and pass first
diffraction order radiation in a second direction toward the
microlithographic substrate, the second direction being inclined at
a diffraction angle relative to the first direction; directing at
least a portion of the radiation impinging on the reticle away from
the first direction and toward the second direction by impinging
the radiation on a reflective surface, inclining a first portion of
the reflective surface relative to a second portion of the
reflective surface, and reflecting the beam from the reflective
surface to an optical element and toward the reticle, with the beam
having a second intensity uniformity less than the first intensity
uniformity; impinging the beam on the reticle; and directing the
beam from the reticle to the radiation sensitive material of the
microlithographic substrate after impinging the beam on the
reticle.
31. The method of claim 30 wherein reflecting the beam to an
optical element includes reflecting the beam through a converging
lens, and wherein impinging the beam on the reticle includes
passing the beam through an aperture in the reticle.
32. The method of claim 30, further comprising scanning the reticle
and the microlithographic substrate relative to each other by
moving the reticle along a reticle path generally normal to the
radiation path proximate to the reticle and moving the
microlithographic substrate along a substrate path in a direction
opposite the reticle and generally normal to the radiation
path.
33. The method of claim 30 further comprising stepping the
microlithographic substrate and the reticle relative to each other
by impinging the radiation on a first field of the
microlithographic substrate while the microlithographic substrate
is in a fixed transverse alignment with the reticle, moving at
least one of the reticle and the microlithographic substrate
transversely relative to the other to align a second field with the
reticle, and exposing the second field to the radiation.
34. The method of claim 30, further comprising exposing a layer of
photoresist material on the microlithographic substrate to the
radiation beam.
35. The method of claim 30, further comprising: directing the
radiation with the second shape along the radiation path toward the
microlithographic substrate; ceasing to impinge the radiation on
the microlithographic substrate while changing a position of the
first portion of the reflective surface relative to the second
portion; and directing from the reflective surface and toward the
microlithographic substrate radiation with a third shape different
than the second shape.
36. The method of claim 30, further comprising changing from the
second shape to a third shape different than the second shape while
the radiation beam impinges on the microlithographic substrate by
moving at least one of the first and second portions of the
reflective surface relative to the other.
37. The method of claim 30 wherein changing a shape of the
radiation beam from a first shape to a second shape different than
the first shape includes changing the shape to at least one of an
annular shape, a dipole shape and a quadrupole shape.
38. The method of claim 30, further comprising changing an
intensity of a first portion of the radiation beam in a plane
generally transverse to the radiation path relative to a second
portion of the radiation beam in the same plane.
39. The method of claim 30 wherein changing the shape of the
radiation beam from a first shape to a second shape includes
changing the shape of the radiation beam to a second shape having a
major axis and a minor axis, and wherein the method further
comprises: directing the radiation beam with the second shape along
the radiation path toward an aperture of a reticle, the aperture
having a major axis and a minor axis; and aligning the major axis
of the second shape of the radiation beam to be at least
approximately parallel with the major axis of the aperture.
40. A method for irradiating a microlithographic substrate,
comprising: positioning a first microlithographic substrate on a
support member; directing a radiation beam along a radiation path
toward the first microlithographic substrate, the radiation beam
having a first shape in a plane generally transverse to the
radiation path; moving a first portion of a reflective surface
relative to a second portion of the reflective surface to define a
first configuration of the reflective surface, correlating the
first configuration with a first pattern of optical features of a
first reticle; changing a shape of the radiation beam from the
first shape to a second shape different than the first shape by
reflecting the radiation beam from the reflective surface while the
reflective surface is in the first configuration; directing the
radiation beam with the second shape to an optical element, to the
first reticle and to the first microlithographic substrate;
replacing the first reticle with a second reticle having a second
pattern of optical features; accommodating differences between the
first reticle and the second reticle by moving the first portion of
the reflective surface relative to the second portion to place the
reflective surface in a second configuration different than the
first configuration; correlating the second configuration with the
second pattern of optical features of the second reticle; changing
a shape of the radiation beam to a third shape different than the
second shape by reflecting the radiation beam from the reflective
surface while the reflective surface is in the second
configuration; and directing the radiation beam with the third
shape to the optical element, to the second reticle and to the
second microlithographic substrate.
41. The method of claim 40, further comprising scanning the reticle
and the microlithographic substrate relative to each other by
moving the reticle along a reticle path generally normal to the
radiation path proximate to the reticle and moving the
microlithographic substrate along a substrate path in a direction
opposite the reticle and generally normal to the radiation
path.
42. The method of claim 40, further comprising stepping the
microlithographic substrate and the reticle relative to each other
by impinging the radiation on a first field of the
microlithographic substrate while the microlithographic substrate
is in a fixed transverse alignment with the reticle, moving at
least one of the reticle and the microlithographic substrate
transversely relative to the other to align a second field with the
reticle, and exposing the second field to the radiation.
43. The method of claim 40, further comprising exposing a layer of
photoresist material on the microlithographic substrate to the
radiation beam.
44. The method of claim 40 wherein changing a shape of the
radiation beam from a first shape to a second shape different than
the first shape includes changing the shape to at least one of an
annular shape, a dipole shape and a quadrupole shape.
45. The method of claim 40, further comprising changing an
intensity of a first portion of the radiation beam in a plane
generally transverse to the radiation path relative to a second
portion of the radiation beam in the same plane.
46. The method of claim 40 wherein changing the shape of the
radiation beam from a first shape to a second shape includes
changing the shape of the radiation beam to a second shape having a
major axis and a minor axis, and wherein the method further
comprises: directing the radiation beam with the second shape along
the radiation path and through an aperture of the first reticle,
the aperture having a major axis and a minor axis; and aligning the
major axis of the second shape of the radiation beam to be at least
approximately parallel with the major axis of the aperture.
47. A method for adjusting an intensity distribution of radiation
directed to a radiation-sensitive material of a microlithographic
substrate, comprising: selecting a target distribution of radiation
angles relative to a reticle plane of a reticle; directing a
radiation beam along a radiation path; reflecting the radiation
beam from a reflective surface, to an optical element and toward a
reticle, the radiation beam having a first intensity uniformity and
a first distribution of radiation angles relative to the reticle;
determining an error between the first distribution and the target
distribution; and until the first distribution is at least
approximately the same as the target distribution, changing the
first distribution by inclining a first portion of the reflective
surface relative to a second portion of the reflective surface to
change a shape of the radiation beam in a plane generally
transverse to the radiation path, and reflecting the radiation to
the optical element toward the reticle, with the beam having a
second intensity uniformity less than the first intensity
uniformity.
48. The method of claim 47 wherein reflecting the radiation beam to
an optical element involves passing the radiation beam through a
converging lens.
49. The method of claim 47, further comprising scanning the reticle
and the microlithographic substrate relative to each other by
moving the reticle along a reticle path generally normal to the
radiation path proximate to the reticle and moving the
microlithographic substrate along a substrate path in a direction
opposite the reticle and generally normal to the radiation
path.
50. The method of claim 47, further comprising stepping the
microlithographic substrate and the reticle relative to each other
by impinging the radiation on a first field of the
microlithographic substrate while the microlithographic substrate
is in a fixed transverse alignment with the reticle, moving at
least one of the reticle and the microlithographic substrate
transversely relative to the other to align a second field with the
reticle, and exposing the second field to the radiation.
51. The method of claim 47, further comprising exposing a layer of
photoresist material on the microlithographic substrate to the
radiation beam.
52. The method of claim 47, further comprising: directing the
radiation with the second shape along the radiation path toward the
microlithographic substrate; ceasing to impinge the radiation on
the microlithographic substrate while changing a position of the
first portion of the reflective surface relative to the second
portion; and directing from the reflective surface and toward the
microlithographic substrate radiation with a third shape different
than the second shape.
53. The method of claim 47, further comprising changing the shape
of the radiation beam from the second shape to a third shape
different than the second shape while the radiation beam impinges
on the microlithographic substrate by moving at least one of the
first and second portions of the reflective surface relative to the
other.
54. The method of claim 47 wherein changing a shape of the
radiation beam from a first shape to a second shape different than
the first shape includes changing the shape to at least one of an
annular shape, a dipole shape and a quadrupole shape.
55. The method of claim 47, further comprising changing an
intensity of a first portion of the radiation beam in a plane
generally transverse to the radiation path relative to a second
portion of the radiation beam in the same plane.
56. The method of claim 47 wherein changing the shape of the
radiation beam from a first shape to a second shape includes
changing the shape of the radiation beam to a second shape having a
major axis and a minor axis, and wherein the method further
comprises: directing the radiation beam with the second shape
through an aperture of a reticle, the aperture having a major axis
and a minor axis; and aligning the major axis of the second shape
of the radiation beam to be at least approximately parallel with
the major axis of the aperture.
57. An apparatus for irradiating a radiation-sensitive material of
a microlithographic substrate, comprising: a support member
configured to releasably support the microlithographic substrate; a
radiation source configured to emit a beam of radiation directed
along a radiation path toward the support member; a reticle
positioned along the radiation path, the reticle being configured
to pass the radiation toward the substrate support; a reflective
surface positioned along the radiation path, the reflective surface
having a first portion and a second portion with the first portion
movable relative to the second portion to change a shape of the
radiation beam in a plane generally transverse to the radiation
path from a first shape and a first intensity uniformity to a
second shape different than the first shape wherein the beam with
the second shape has a second intensity uniformity less than the
first intensity uniformity; an optical element positioned between
the reflective surface and the support member to receive radiation
from the reflective surface and direct at least some of the
radiation at an angle relative to the radiation path; and a
controller operatively coupled to the reflective surface, the
controller being configured to direct the first portion of the
reflective surface to move relative to the second portion to change
the shape of the radiation beam from the first shape to the second
shape.
58. The apparatus of claim 57 wherein the first portion of the
reflective surface forms a smooth, continuous surface with the
second portion of the reflective surface.
59. The apparatus of claim 57 wherein the first portion of the
reflective surface includes a first reflective element and the
second portion of the reflective surface includes a second
reflective element movable independently from the first reflective
element.
60. The apparatus of claim 57 wherein the reticle is coupled to a
reticle actuator to move along a reticle path generally normal to
the radiation path proximate to the reticle, and wherein the
support member is coupled to a support member actuator to move
along a support member path in a direction opposite the reticle and
generally normal to the radiation path.
61. The apparatus of claim 57 wherein at least one of the support
member and the reticle is coupled to at least one actuator to
sequentially align fields of the microlithographic substrate with
the radiation beam when the microlithographic substrate is carried
by the support member.
62. The apparatus of claim 57 wherein the reticle has at least one
reticle aperture positioned to pass the radiation beam toward the
microlithographic substrate, and wherein the optical element
includes a converging lens configured to direct at least part of
the radiation beam at an angle relative to the radiation path.
63. An apparatus for irradiating a radiation-sensitive surface of a
microlithographic substrate, comprising: a support member
configured to releasably support the microlithographic substrate; a
radiation source configured to emit a beam of radiation along a
radiation path directed toward the support member; a reticle
positioned along the radiation path between the radiation source
and the support member, the reticle being positioned to pass the
radiation toward the substrate support; a reflective surface
positioned along the radiation path between the reticle and the
radiation source, the reflective surface having a first portion and
a second portion with the first portion movable relative to the
second portion to change a shape of the radiation beam in a plane
generally transverse to the radiation path from a first shape and a
first intensity uniformity to a second shape different than the
first shape wherein the beam with the second shape has a second
intensity uniformity less than the first intensity uniformity; an
optical element positioned between the reflective surface and the
support member to receive radiation from the reflective surface and
direct at least some of the radiation at an angle relative to the
radiation path; and a controller operatively coupled to the
reflective surface, the controller being configured to direct the
first portion of the reflective surface to move relative to the
second portion to change the shape of the radiation beam from the
first shape to the second shape.
64. The apparatus of claim 63 wherein the first portion of the
reflective surface forms a smooth, continuous surface with the
second portion of the reflective surface.
65. The apparatus of claim 63 wherein the first portion of the
reflective surface includes a first reflective element and the
second portion of the reflective surface includes a second
reflective element movable independently from the first reflective
element.
66. The apparatus of claim 63 wherein the reticle is coupled to a
reticle actuator to move along a reticle path generally normal to
the radiation path proximate to the reticle, and wherein the
support member is coupled to a support member actuator to move
along a support member path in a direction opposite the reticle and
generally normal to the radiation path.
67. The apparatus of claim 63 wherein at least one of the support
member and the reticle is coupled to at least one actuator to
sequentially align fields of the microlithographic substrate with
the radiation beam when the microlithographic substrate is carried
by the support member.
68. The apparatus of claim 63 wherein the reticle has at least one
reticle aperture positioned to pass the radiation beam toward the
microlithographic substrate, and wherein the optical element
includes a converging lens configured to direct at least part of
the radiation beam at an angle relative to the radiation path.
69. The method of claim 1 wherein impinging the beam on the
microlithographic substrate includes impinging the beam with a
monotonically varying intensity distribution.
70. The method of claim 1 wherein impinging the beam on the
microlithographic substrate includes impinging the beam with a
non-monotonically varying intensity distribution.
71. The method of claim 1 wherein impinging the beam includes
impinging a first beam region having a generally uniform intensity
distribution spaced apart from a second beam region having a
generally uniform intensity distribution.
Description
BACKGROUND
The present invention is directed toward methods and apparatuses
for shaping and/or orienting radiation directed toward a
microlithographic substrate. Microelectronic features are typically
formed in microelectronic substrates (such as semiconductor wafers)
by selectively removing material from the wafer and filling in the
resulting openings with insulative, semiconductive, or conductive
materials. One typical process includes depositing a layer of
radiation-sensitive photoresist material on the wafer, then
positioning a patterned mask or reticle over the photoresist layer,
and then exposing the masked photoresist layer to a selected
radiation. The wafer is then exposed to a developer, such as an
aqueous base or a solvent. In one case, the photoresist layer is
initially generally soluble in the developer, and the portions of
the photoresist layer exposed to the radiation through patterned
openings in the mask change from being generally soluble to become
generally resistant to the developer (e.g., so as to have low
solubility). Alternatively, the photoresist layer can be initially
generally insoluble in the developer, and the portions of the
photoresist layer exposed to the radiation through the openings in
the mask become more soluble. In either case, the portions of the
photoresist layer that are resistant to the developer remain on the
wafer, and the rest of the photoresist layer is removed by the
developer to expose the wafer material below.
The wafer is then subjected to etching or ion implantation
processes. In an etching process, the etchant removes exposed
material, but not material protected beneath the remaining portions
of the photoresist layer. Accordingly, the etchant creates a
pattern of openings (such as grooves, channels, or holes) in the
wafer material or in materials deposited on the wafer. These
openings can be filled with insulative, conductive, or
semiconductive materials to build layers of microelectronic
features on the wafer. The wafer is then singulated to form
individual chips, which can be incorporated into a wide variety of
electronic products, such as computers and other consumer or
industrial electronic devices.
When the photoresist layer is exposed to radiation, the radiation
passing through the apertures of the mask or reticle diffracts to
form a diffraction pattern that is collected by an optic system and
projected onto the photoresist layer. The imaged or projected
diffraction pattern defines the features formed in the photoresist
layer. Accordingly, the radiation can form a central or zeroth
diffraction order, a first diffraction order positioned outwardly
on each side of the zeroth order, and possibly second or higher
diffraction orders disposed outwardly from the first orders. The
smaller the aperture in the reticle, the greater the angle between
the zeroth diffraction order and the first diffraction order. If
the aperture is reduced in size (for example, to reduce the size of
the features in the wafer), the first diffraction order may spread
out so far from the zeroth order that it is no longer captured by
the optic system and projected onto the photoresist layer. This can
adversely affect the quality of image formed on the photoresist
layer because the first diffraction order is generally required to
adequately define the image projected onto the photoresist
layer.
One approach to addressing the foregoing problem is to direct the
radiation beam incident on the reticle aperture at an angle
relative to the optical axis using a series of optical elements
positioned between the radiation source and the reticle. For
example, the optical elements (optionally in conjunction with a
blade) can form a radiation beam that initially has an annular
cross-sectional shape and is directed generally parallel to the
optical axis. The radiation beam then passes through a series of
optical elements that direct the radiation at an angle to the
optical axis. Accordingly, the radiation incident on the reticle
aperture will pass through the aperture at an angle. This can
effectively tilt the diffraction pattern. As a result, this method
can improve the likelihood for capturing one of the first
diffraction orders, possibly at the expense of the other.
One drawback with the foregoing approach is that the lenses that
shape the radiation beam can have aberrations that adversely affect
the quality of the images they produce. One general approach to
correcting lens aberrations in wafer optic systems (disclosed in
U.S. Pat. No. 5,142,132 to McDonald et al.), is to reflect the
radiation beam from a deformable mirror, which can be adjusted to
correct for the aberrations in the lens optics.
However, another drawback with the beam-shaping lens system is that
it is relatively inflexible. Accordingly, it is difficult to
adequately tailor the beam shape (and therefore the resulting
incidence angle of the radiation) to different reticle apertures or
aperture patterns because the number of available beam shapes for a
given optics system may be limited, and it may be time consuming to
change one optics system or system set-up for another.
SUMMARY
The present invention is directed to methods and apparatuses for
shaping radiation directed to a microlithographic substrate. In one
aspect of the invention, the method can include directing a beam of
radiation along a radiation path toward a reflective medium, with
the beam having a first shape in a plane generally transverse to
the radiation path. The method can further include changing a shape
of the radiation beam from the first shape to a second shape
different than the first shape by inclining a first portion of the
reflective medium relative to a second portion of the reflective
medium, and reflecting the beam from the reflective medium toward a
microlithographic substrate. The method can still further include
impinging the beam on the microlithographic substrate after
changing the shape from the first shape to the second shape.
In a further aspect of the invention, the radiation beam can have a
first intensity prior to impinging on the reflective medium and the
method can further include directing the radiation beam away from
the reflective medium with the second shape and with a second
intensity at least approximately the same as the first intensity.
The method can still further include changing an angle of at least
a portion of the radiation relative to the radiation path by
impinging the radiation beam on an optical element after changing
the shape of the beam from the first shape to the second shape.
The invention is also directed toward an apparatus for irradiating
a radiation-sensitive surface of a microlithographic substrate. The
apparatus can include a support member configured to releasably
support the microlithographic substrate, and a radiation source
configured to emit a beam of radiation along a radiation path
directed toward the support member. A reticle is positioned along
the radiation path and is configured to pass the radiation toward
the substrate support. A reflective medium is also positioned along
the radiation path and has a first portion and a second portion
with the first portion movable relative to the second portion to
change a shape of the radiation beam in a plane generally
transverse to the radiation path from a first shape to a second
shape different than the first shape. An optical element can be
positioned between the reflective medium and the support member to
receive radiation from the reflective medium and direct at least
some of the radiation at an angle relative to the radiation path. A
controller can be operatively coupled to the reflective medium and
can be configured to direct the first portion of the reflective
medium to move relative to the second portion to change the shape
of the radiation beam from the first shape to the second shape.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an illustration of an apparatus in accordance with an
embodiment of the invention with components shown
schematically.
FIG. 2A is a schematic illustration of a portion of the apparatus
shown in FIG. 1 with a radiation beam incident on a reticle at a
normal angle in accordance with an embodiment of the invention.
FIG. 2B is a schematic illustration of a portion of the apparatus
shown in FIG. 1 with a radiation beam incident on a reticle at an
oblique angle in accordance with another embodiment of the
invention.
FIG. 3A is a schematic illustration of a portion of the apparatus
shown in FIG. 1 in accordance with an embodiment of the
invention.
FIGS. 3B-C schematically illustrate radiation beams having
distributions of radiation angles produced by an embodiment of the
apparatus shown in FIG. 3A.
FIGS. 4A-E schematically illustrate shapes of radiation beams
produced in accordance with further embodiments of the
invention.
FIG. 5 is a flow diagram illustrating a method for configuring
radiation directed to microlithographic substrates in accordance
with an embodiment of the invention.
DETAILED DESCRIPTION
The present disclosure describes methods and apparatuses for
shaping and/or orienting radiation beams directed toward
microlithographic substrates. The term "microlithographic
substrate" is used throughout to include substrates upon which
and/or in which microelectronic circuits or components, data
storage elements or layers, vias or conductive lines, micro-optic
features, micromechanical features, and/or microbiological features
are or can be fabricated using microlithographic techniques. Many
specific details of certain embodiments of the invention are set
forth in the following description and in FIGS. 1-5 to provide a
thorough understanding of these embodiments. One skilled in the
art, however, will understand that the present invention may have
additional embodiments, and that the invention may be practiced
without several of the details described below.
FIG. 1 schematically illustrates an apparatus 110 for shaping
radiation directed to a microlithographic substrate 160 in
accordance with an embodiment of the invention. The apparatus 110
can include an electromagnetic radiation source 120 that directs a
radiation beam 128 along a radiation path (or optical axis) 180
toward the microlithographic substrate 160. The radiation beam 128
can be shaped by a reflective medium 140 having a movable
reflective surface 145, and can be at least partially diffracted or
diffused by a diffractive optical element or diffuser 112. A
collecting lens 113 can collect the radiation from the diffuser 112
and direct it at an angle to the radiation path 180. Optionally,
the apparatus 110 can further include a light tube 124 positioned
to generate a plurality of images of the radiation source 120. The
light tube 124 and/or a sizing lens 125 can size the radiation beam
128 which can then be directed by a mirror 126 through a focusing
lens 127 to a reticle or mask 130. The radiation beam 128 impinging
on the reticle 130 can also be inclined at an angle relative to the
radiation path 180, as described in greater detail below with
reference to FIGS. 2B-4E.
In one embodiment, the reticle 130 can include reticle apertures
131 through which the radiation beam 128 passes to form an image on
the microlithographic substrate 160. Prior to impinging on the
microlithographic substrate 160, the radiation beam 128 passes
through a reduction lens 111 which reduces the size of the image
pattern defined by the reticle 130 to correspond to the size of the
features to be formed on the microlithographic substrate 160. The
radiation beam 128 can then emerge from the reduction lens 111 to
impinge on a radiation-sensitive material (such as a photoresist
layer 161) of the microlithographic substrate 160 and form an image
on the layer 161.
In one embodiment, the radiation beam 128 can have a width of from
about 5 mm. to about 8 mm. and a length (transverse to the plane of
FIG. 1) of about 26 mm at the microlithographic substrate 160. In
other embodiments, the radiation beam 128 can have other
dimensions. The radiation emitted by the source 120 can have a
wavelength in the range of about 157 nanometers or less (for
example, 13 nanometers) to a value of about 365 nanometers or more.
For example, the radiation can have a wavelength of about 193
nanometers. In other embodiments, the radiation can have other
wavelengths suitable for exposing the layer 161 on the
microlithographic substrate 160.
The microlithographic substrate 160 is supported on a substrate
support 150. In one embodiment (a scanner arrangement), the
substrate support 150 moves along substrate support path 151, and
the reticle 130 moves in the opposite direction along a reticle
path 132 to scan the image produced by the reticle 130 across the
layer 161 while the position of the radiation beam 128 remains
fixed. Accordingly, the substrate support 150 can be coupled to a
support actuator 154, and the reticle 130 can be coupled to a
reticle actuator 137. As the reticle 130 moves opposite the
substrate support 150 and the microlithographic substrate 160, the
radiation source 120 can flash to irradiate successive portions of
the microlithographic substrate 160 with corresponding successive
images produced by the reticle 130, until an entire field of the
microlithographic substrate 160 is scanned. In one embodiment, the
radiation source 120 can flash at a rate of about 20 cycles during
the time required for the microlithographic substrate 160 to move
by one beam width (e.g., from about 5 mm. to about 8 mm.). In other
embodiments, the radiation source 120 can flash at other rates. In
any of these embodiments, the radiation source 120 can flash at the
same rate throughout the scanning process (assuming the reticle 130
and the substrate support 150 each move at a constant rate) to
uniformly irradiate each field of the microlithographic substrate
160. Alternatively, the radiation source 120 can deliver a
continuous radiation beam 128. In any of these embodiments, each
field can include one or more dice or chips, or alternatively, each
field can include other features.
In another embodiment (a stepper arrangement), the radiation beam
128 and the reticle 130 can expose an entire field of the
microlithographic substrate 160 in one or more flashes, while the
reticle 130 and the substrate support 150 remain in a fixed
transverse position relative to the radiation path 180. After the
field has been exposed, the reticle 130 and/or the substrate
support 150 can move transverse to the radiation path 180 to expose
another field. This process can be repeated until each field of the
microlithographic substrate 160 is exposed. In one embodiment, each
field can include a single microelectronic chip or die, and in
another embodiment, each field can include more than one die.
In a further aspect of the foregoing embodiments, a controller 170
is operatively coupled to the reticle 130 (or the reticle actuator
137) and the substrate support 150 (or the support actuator 154).
Accordingly, the controller 170 can control and coordinate the
relative movement between these elements. The controller 170 can
also be operatively coupled to the reflective medium 140 to control
the shape of the radiation beam 128, as described in greater detail
below.
FIG. 2A schematically illustrates a portion of the apparatus 110
with the radiation beam 128 impinging on the reticle aperture 131
in a direction generally aligned with the radiation path 180 and
generally normal to the plane of the reticle 130. Accordingly, the
radiation can produce a zeroth diffraction order 133a generally
aligned with the radiation path 180, and first diffraction orders
133b and 133c spaced outwardly from the zeroth diffraction order
133a. This arrangement can be suitable for larger apertures 131, or
isolated apertures 131, both of which tend not to have the first
diffraction orders 133b and 133c spread out substantially from the
zeroth diffraction order 133a. If the first diffraction orders 133b
and 133a are spread out significantly from the zeroth order pattern
133a, they may not be captured by the reduction lens 111, and may
not impinge on the layer 161.
FIG. 2B schematically illustrates a portion of the apparatus 110
shown in FIG. 1 in which at least a portion of the radiation beam
128 is inclined relative to the radiation path 180. Accordingly,
this portion of the radiation beam 128 strikes the reticle 130 at a
non-normal (i.e., oblique) angle to impart an angular shift to
zeroth and first diffraction orders 233a-c. As a result, the zeroth
diffraction order 233a is inclined relative to the radiation path
180, unlike the zeroth diffraction order 133b described above with
reference to FIG. 2A. The right-most first diffraction order 233b
is inclined relative to the radiation path 180 at a shallower angle
than the corresponding first diffraction order 133b described above
with reference to FIG. 2A. The left-most first diffraction order
233c is inclined at a greater angle than the corresponding first
diffraction order 133c described above with reference to FIG. 2A.
Accordingly, the left-most first diffraction order 233c may not be
captured by the reduction lens 111. However, both the zeroth
diffraction order 233a and the right-most first diffraction order
233b can be captured by the reduction lens 111. Accordingly, this
arrangement can be suitable for non-isolated apertures 131 or
smaller apertures 131, both of which tend to have first diffraction
orders spread apart substantially from the zeroth diffraction
order, and for which neither first diffraction order may be
captured by the reduction lens 111 if the radiation were to strike
the reticle 130 at a normal angle as shown in FIG. 2A.
FIGS. 3A-C schematically illustrate how an embodiment of the
apparatus 110 shown in FIG. 1 can produce radiation that is
inclined relative to the reticle 130 and the radiation path 180 in
the manner described above with reference to FIG. 2B. FIG. 3A
schematically illustrates a sectional view through the reflective
medium 140, the diffuser 112, and the collecting lens 113 described
above with reference to FIG. 1 in accordance with an embodiment of
the invention. In one aspect of this embodiment, the reflective
medium 140 can include a two-dimensional array of reflective
elements 141, each coupled to an actuator 142 and defining the
reflective surface 145. Reflective (or optionally non-reflective)
material can be positioned in the interstices between adjacent
reflective elements 141. Alternatively, the reflective medium 140
can include a continuous deformable reflective surface coupled to
the actuators 142. In either embodiment, the actuators 142 can be
coupled to the controller 170, which can direct each actuator 142
to tilt its corresponding reflective element 141 (or portion of the
reflective surface 145) to a selected angle relative to incident
radiation arriving from the radiation source 120. Accordingly, the
reflective medium 140 can alter the path of the incoming radiation
to form any arbitrary shape at the diffuser 112. In one aspect of
this embodiment, the reflective medium 140 can be positioned far
enough away from the diffuser 112 so that radiation arriving at the
diffuser 112 can be generally parallel to the radiation path 180.
The diffuser 112 can then diffuse the radiation arriving from the
reflective medium 140 to smooth out potential discontinuities in
the radiation beam 128. The collecting lens 113 can collect the
radiation from the diffuser 112 and incline the radiation at an
angle A relative to the radiation path 180, as described in greater
detail below.
In one aspect of this embodiment, the shape of the radiation beam
128 incident upon and exiting the diffuser 112 can be generally
annular, with a radius R varying from an inner radius R.sub.1 to an
outer radius R.sub.2 and with the radiation aligned generally
parallel with the radiation path 180. The collecting lens 113 can
collect the radiation from the diffuser 112 and direct it toward
the light tube 124 (or another optical element) with the radiation
converging toward the radiation path 180 at an angle A that varies
from an inner angle A.sub.1 to an outer angle A.sub.2. As the
radius R increases, angle A also increases. Accordingly, radiation
toward the periphery of the annulus has a higher inclination angle
A than radiation toward the center of the annulus. If the annulus
defines a relatively narrow band (i.e., if the distance between
R.sub.1 and R.sub.2 is relatively small), the angular orientation
of the radiation will tend to be concentrated in a narrow range of
angles A. If the annulus defines a relatively broad band (i.e., if
the distance between R.sub.1 and R.sub.2 is relatively large), the
angular orientation of the radiation will tend to be distributed
over a wider range of angles A. In either embodiment, the optics
system between the collecting lens 113 and the reticle 130 can
either further alter the distribution of the radiation inclination
angles A across the radiation beam 128, or maintain approximately
the same distribution.
FIG. 3B is a cross-sectional view of the radiation beam 128 taken
substantially along line 3B--3B of FIG. 3A illustrating the annular
shape of the radiation beam 128 in accordance with an embodiment of
the invention. FIG. 3C schematically illustrates in side view the
radiation beam 128 as it strikes the reticle 130 proximate to the
reticle aperture 131 For purposes of illustration, the radiation
beam 128 is shown in FIG. 3C as including some beamlets inclined at
an angle +A relative to the radiation path 180, and some beamlets
inclined at an angle -A relative to the radiation path 180. In
actuality, the beam 128 can include beamlets describing a
distribution of inclination angles that depends upon the shape and
size of the beam impinging on the collecting lens 113, as described
above with reference to FIG. 3A. Because the beamlets are inclined
relative to the radiation path 180, they can emphasize selected
diffraction orders at the expense of others, generally as described
above with reference to FIG. 2B. For example, the beamlets oriented
at angle +A can emphasize the +1 diffraction order at the expense
of the -1 diffraction order, and the beamlets oriented at angle -A
can emphasize the -1 diffraction order at the expense of the +1
diffraction order. In other embodiments, the orientation of the
radiation in the beam 128 can be selected to emphasize other
diffraction orders, and/or can have other shapes or arrangements,
as described in greater detail below with reference to FIGS.
4A-4E.
FIGS. 4A-4E illustrate cross-sectional views of other beam shapes
that can be produced by adjusting the relative positions of one or
more portions of the reflective medium 140 (FIG. 3A). For example,
as shown in FIG. 4A, a beam 428a can have a dipole shape with two
arcuate dipoles 443. The dipoles 443 can be aligned along a major
axis 444a and transverse to a minor axis 444b. In a further aspect
of this embodiment, the major axis 444a can be at least
approximately aligned with a corresponding major axis of an
elongated reticle aperture 431, shown superimposed on the beam
shape of FIG. 4A for purposes of illustration. Accordingly, the
shape of the beam produced by the reflective medium 140 can be
tailored to the shape of the aperture in the reticle 130, and
correspondingly, the shape of the image printed on the
microlithographic substrate 160. In a further aspect of this
embodiment, at least some of the radiation can be directed into
interstitial regions 443a to irradiate other reticle apertures
having a major axis generally aligned with the minor axis 444b. The
intensity of the radiation directed to the interstitial regions
443a can be less than that directed to the dipoles 443 when the
radiation intensity requirements for apertures aligned with the
minor axis 444b are less than those for apertures aligned with the
major axis 444a.
In other embodiments, the beam can have other shapes. For example,
as shown in FIG. 4B, a beam 428b can have a quadrupole shape with
four quadrupole regions 445. Each quadrupole region 445 can direct
the radiation toward the collecting lens (FIG. 3A), which can then
incline the radiation relative to the radiation path 180, in a
manner generally similar to that described above. FIG. 4C
illustrates a beam 428c having a shape corresponding to that
described above with reference to FIG. 2A. Accordingly, the
radiation incident on the reticle 130 proximate to the reticle
aperture 131 is at least approximately normal.
FIG. 4D illustrates a radiation beam 428d having an intensity
distribution altered from that of the beam as it impinges on the
reflective medium 140 (FIG. 1). For example, the overall intensity
of the radiation beam 428d can be the same as that of the beam as
it impinges the reflective medium 140, but the intensity of the
reflected beam can be greater toward the center of the beam 428d
than toward the periphery of the beam 428d. This effect can be
achieved by adjusting the angular position of the reflective
elements 141 (FIG. 3A) to direct more of the incident light to the
center of the diffuser 112 and the collecting lens 113 (FIG. 3A)
than to the periphery of the diffuser 112 and the collecting lens
113. Accordingly, the intensity of the radiation beam 428d can
provide additional control over the illumination of the
microlithographic substrate 160. For example, by increasing the
intensity of radiation toward the center of the beam 428d, this
arrangement can emphasize the effect of radiation that is more
closely aligned with radiation path 180 (i.e., has a relatively
small angle A), relative to radiation that diverges more
significantly from the radiation path 180. FIG. 4E illustrates a
radiation beam 428e having a dipole configuration, also with a
variation in intensity across the cross-section of the beam. For
any of the foregoing embodiments, the radius R of any position in
the radiation beam impinging on the diffuser 112 and the collecting
lens 113 can correlate with the angle A at which the radiation
exiting the collecting lens 113 is oriented relative to the
radiation path 180, as described above with reference to FIG.
3A.
One feature of several of the embodiments described above with
reference to FIGS. 1-4E is that the reflective medium 140 can
change the shape of the radiation beam to any arbitrary
configuration. This feature, particularly in combination with the
collecting lens 113 (and, optionally, the diffuser 112), can be
used to adjust the angle at which the radiation strikes the reticle
aperture 131. By controlling the angle at which the radiation
impinges on the reticle, the apparatus can control the diffractive
orders that ultimately impinge on the microlithographic substrate
160. One advantage of this feature is that the reflective medium
140 can be simpler than the array of lenses that would
conventionally be required to form a radiation beam having the same
shape. The simpler reflective medium 140 can reduce the cost of
producing shaped radiation beams, and can also improve the optical
efficiency of the radiation beam because the beam need not pass
through as great a number of lenses or other optical elements.
Another advantage of this feature is that the reflective medium 140
can be easily and quickly adjusted to produce an almost infinite
variety of radiation beam shapes and corresponding radiation
inclination angles. For example, the reflective medium 140 can be
adjusted in a fraction of a second. This is unlike some
conventional arrangements that require 20 seconds or even
substantially longer to adjust. Accordingly, the same reflective
medium 140 can remain in the optical system and can be adjusted
(for example, with the controller 170) depending on the pattern,
size and configuration of the apertures 131 and the reticle 130.
This arrangement can simplify the task of changing the beam
inclination angle when one reticle having a particular arrangement
of reticle apertures 131 is exchanged for another reticle having a
different arrangement of reticle apertures. Alternatively, the
reflective surface can change the shape of the beam 128 as the
reticle 130 and the microlithographic substrate 160 scan relative
to each other. For example, the reflective medium 140 can be
configured to generate a radiation beam 128 having a first shape
while the radiation beam irradiates reticle apertures having a
corresponding first shape. When the reticle 130 moves to a position
that aligns with the beam 128 with reticle apertures having a
second, different shape, the reflective medium 140 can change the
shape of the beam accordingly.
Still a further advantage of this feature is that the reflective
medium 140 can account for other variations in the characteristics
of the process implemented to form images on the microlithographic
substrate 160. For example, different reticles 130 configured to
have reticle apertures 131 of the same pattern and size may in fact
have slightly different reticle apertures 131 due to manufacturing
tolerances associated with the production of the reticles
themselves. The reflective medium 140 can be adjusted to account
for such differences. The reflective medium 140 can also be
adjusted to account for differences in other features of the system
110, such as the lenses or other optical features, and/or
variations from one microlithographic substrate 160 to the next or
one photoresist layer 161 to the next.
Still another advantage of the foregoing feature is that the
overall intensity of the radiation beam 128 reflected from the
reflective medium 140 can be at least approximately the same as the
overall intensity of the radiation beam 128 incident on the
reflective medium 140. This is so even if the reflective medium 140
is configured to redistribute the radiation intensity (as described
above with reference to FIGS. 4D-E). Accordingly, the foregoing
arrangement can form shaped radiation beams without significantly
compromising overall intensity, as would occur if a plate having a
cut-out with the desired beam shape were interposed between the
radiation source 120 and the microlithographic substrate 160. By
preserving the incident radiation intensity, the foregoing
arrangement can be used to irradiate the microlithographic
substrate 160 in the manner described above without decreasing the
process throughput by increasing the time required to adequately
expose the microlithographic substrate 160 to the radiation.
Another advantage of the foregoing arrangement is that the
reflective medium 140 can flexibly control the intensity of the
radiation as a function of the angle between the radiation and the
radiation path. Accordingly, the arrangement can increase the
intensity of a portion of the radiation at a selected inclination
angle (or range of radiation angles) when it is desirable to
emphasize the characteristics of the image produced by the
radiation at that angle (or range of angles). The intensity
distribution can be readily changed (by changing the orientation of
the reflective elements 141) when it is desirable to emphasize the
effects of radiation at a different angle or range of angles.
Yet a further advantage of this arrangement is that the reflective
medium 140 can be iteratively adjusted until the radiation beam
shape (and therefore the desired distribution of radiation
incidence angles at the reticle) is attained. For example, a user
can adjust the reflective medium 140 to produce a first beam shape
and then evaluate the effect on a microlithographic substrate 160.
If the effect is not the desired effect, the configuration of the
reflective medium 140 can be further adjusted (without replacing a
complex lens system) until the desired effect is achieved.
FIG. 5 is a flow chart illustrating an iterative process 500 in
accordance with an embodiment of the invention. In one aspect of
this embodiment, the process can include compiling design data for
a reticle (step 502), building and analyzing a reticle (step 504),
and setting up an exposure process (step 505). In parallel, the
design data compiled in step 502 can optionally be input into a
lithography simulator in step 508 to calculate initial irradiation
conditions for high quality critical images of the
microlithographic substrate. Suitable lithography simulators are
available from KLA Tencor of San Jose, Calif. and Sigma-C of
Munich, Germany. In step 510, the process can optionally include
revising the illumination conditions to compensate for reticle
and/or device parameter errors. Optionally, this step can include
using data obtained from the analysis completed in step 504. In one
embodiment, the errors can be attributed to a dense concentration
of microlithographic features. Alternatively, the errors can be
attributed to isolated microlithographic features. In still further
embodiments, the errors can be attributed to other features. In any
of these embodiments, the process can further include setting the
configuration of the reflective medium with the controller in step
512, and then printing an image on a photoresist layer of the
microlithographic substrate (step 506) using the reticle
configuration established in step 505, along with the reflective
medium configuration established in step 512.
In step 514, the microlithographic substrate can be processed to a
selected analysis step. In step 516, the process can include
measuring selected device feature characteristics and determining
deviations (if any) from target characteristics of these features.
In step 518, the process can include determining whether the
deviations are within acceptable limits. If the deviations are
within acceptable limits, the process can end. Alternatively, if
the deviations are not within acceptable limits, an error between
the measured characteristics and the target characteristics can be
calculated and used to modify the configuration of the reflective
medium. In one aspect of this embodiment, the lithography simulator
can be used to aid in determining the updated reflective medium
configuration. This iterative process can be repeated until the
measured characteristics deviate from the target characteristics by
no more than an acceptable amount.
From the foregoing, it will be appreciated that specific
embodiments of the invention have been described herein for
purposes of illustration, but that various modifications may be
made without deviating from the spirit and scope of the invention.
For example, any of the refractive elements described above,
including the reticle, can be replaced with reflective elements
that perform generally the same function. Accordingly, the
invention is not limited except as by the appended claims.
* * * * *